1. Field of the Invention
In general, the present invention relates to an intensive management apparatus for managing a time-sharing multiplexing network. More particularly, the present invention relates to an intensive management apparatus for checking validity of paths in a time-sharing multiplexing network.
2. Description of the Related Art
In many cases, a network used in an enterprise or the like is implemented by a time-sharing multiplexing network such as an SDH (Synchronous Digital Hierarchy) network. A time-sharing multiplexing network is a network in which a frame is transmitted through a plurality of time slots each allocated to transmitted data. A time-sharing multiplexing network is composed of a plurality of terminals, a plurality of communication apparatuses and transmission lines connecting the communication apparatuses to each other. A terminal is typically a personal computer accommodated by a communication apparatus directly or through a multiplexing apparatus or the like. By means of a cross-connect unit and in accordance with line-setting information, a communication apparatus outputs transmitted data to a transmission line by mapping the data onto time slots allocated to the communication apparatus and the transmission line. The line-setting information is information on time slots used for cross-connecting and multiplexing transmitted data mapped onto the time slots allocated to the communication apparatus and the transmission line.
FIG. 27 is a diagram showing typical paths from a terminal to another terminal. Assume, for example, that paths are set between a terminal 2#11 accommodated by a communication apparatus 12#1 to a terminal 2#21 accommodated by a communication apparatus 12#2. As shown in the figure, the communication apparatus 12#i, where i=1 and 2, comprises a terminal IF unit 14#ij where j=1, 2 and so on, an external IF unit 16#i, a multiplexing unit 18#i, a cross-connect unit 20#i and a transmission-line IF unit 22#ij. A connection point is a conceptual point in the connection between 2 units such as a multiplexing unit 18#i and a cross-connect unit 20#i. At the connection point between 2 units, time slots are allocated to data transmitted between the 2 units. In a communication apparatus 12#i shown in FIG. 27, a symbol Sij denotes a connection point between a terminal IF unit 14#ij and a multiplexing unit 18#i, a symbol Xi denotes a connection point between a multiplexing unit 18#i and a cross-connect unit 20#i, a symbol Lij denotes a connection point between a cross-connect 20#i and a transmission-line IF unit 22#ij and a symbol LN1 denotes a connection point of a transmission line 24#12 between transmission-line IF units 22#ij. In an external interface apparatus 4#i, a symbol CXi denotes a connection point between a multiplexing unit 8#i and an external IF unit 10#i whereas a symbol CSij denotes a connection point between a multiplexing unit 8#i and a terminal IF unit 6#ij.
In order to allow paths between terminals to be set, paths are modified or subjected to other operations with a high degree of flexibility in a time-sharing multiplexing network. The paths each finely set between connection points are connected to allow a route to be configured as a whole between the terminals. For example, a route can be set between the terminals 2#11 and 2#21 by formation of path information P1 describing a path connecting the connection point S11 to the connection point X1, path information P2 describing a path connecting the connection point X1 to the connection point X2 and path information P3 describing a path connecting the connection point X2 to the connection point S21. A person in charge of system management sets information on allocation of time slots at all connection points included in the 3 pieces of path information P1, P2 and P3 in the intensive management apparatus. The intensive management apparatus generates information on line setting based on the information on allocation of time slots. The intensive management apparatus carries out line setting by downloading the information on line setting to the communication apparatuses 12#i. In the conventional time-sharing multiplexing network, however, the following problems are encountered.                (1) The width W2 of allocation of time slots in path information P2 describing a path between the terminating connection points X1 and X2 is different from the width W1 of allocation of time slots in path information P1 between the terminating connection points S11 and X1, that is, W2≠W1. In this case, at a connection point X1 of a communication apparatus 12#1, there is a discrepancy in time-slot-allocation width. Assume that W1>W2. In this case, data transmitted from the terminal 2#11 at a transmission rate corresponding to the width W1 of allocation of time slots is transmitted by the cross-connect unit 20#i at a transmission rate corresponding to the width W2 of allocation of time slots so that the transmitted data is inadvertently destroyed. As a result, an abnormality is generated in the transmitted data between the terminals 2#11 and 2#21.        (2) If the position of an allocated time slot used in the path information P1 is shifted from the position of an allocated time slot used in the path information P2, there will be a discrepancy in time-slot-allocation position at the connection point X1 in the communication apparatus 12#1. The cross-connect unit 20#i allocates a route to transmitted data mapped onto a time slot at the position of the allocated time slot allocated to the path described by the path information P1. Thus, if the position of an allocated time slot allocated to the path described by the path information P1 is different from the position of an allocated time slot allocated to the path described by the path information P2, the data transmitted by the terminal 2#11 and mapped onto the time slot at the position of the allocated time slot at the connection point X1 allocated to the path described by the path information P1 cannot be subjected to route allocation to a time slot at the position of an allocated time slot at the connection point X1 allocated to the path described by the path information P2. As a result, an abnormality is generated in the transmitted data between the terminals 2#11 and 2#21.        (3) If a link of pieces of information on paths between the terminals 2#11 and 2#21 is broken, it is not possible to establish a communication between the terminals 2#11 and 2#21. Likewise, when a path is set between the terminals 2#11 and 2#22, information-on a path between the connection points X2 and S23 may not be set due to a mistake made by the person in charge of network management. In this case, an abnormality is generated between the terminals 2#11 and 2#22.        (4) If the terminal-I/F category of the terminal-IF connection type of the terminal IF unit 14#11 is different from the terminal-I/F category of the terminal-IF connection type of the terminal IF unit 14#21, an abnormality is unavoidably generated between the terminals 2#11 and 2#21.        
If information defining a sequence of lines is formed as information on paths, which is split by a plurality of connection points, as described above, each information on a path is managed as independent path information. A plurality of pieces of path information is then connected to each other to form single path information and the validity of the single path information is checked. Otherwise, the operation of the system will be started inevitably by using incorrect information defining lines.
It is thus an object of the present invention to provide an intensive management apparatus capable of preventing the operation of the system from being started on the basis of incorrect information defining lines by connecting a plurality of pieces of information on a path to each other to form single path information and checking the validity of the single path information when forming the single path information from the pieces of information on a path.